Frac pump system

ABSTRACT

An electric drive pump system includes a power end and a detachable transmission assembly. The transmission assembly is mounted to the power end and is configured to provide rotational power to the power end through a plurality of electric motors. The plurality of electric motors use a gearbox to drive an output spline that engages the power end. A control module is used to regulate the performance characteristics of the plurality of electric motors. A temperature regulation assembly is configured to regulate the temperature of the transmission assembly and the power end.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/647,832 filed Mar. 16, 2020, entitled “Electric Drive Pumpfor Well Stimulation,” which claims benefit of priority under 35 U.S.C.§ 371 to PCT/US2018/052755 filed Sep. 25, 2018, entitled “Electric DrivePump for Well Stimulation,” claiming benefit of priority to UnitedStates Provisional Patent Application Nos. 62/562,943 filed Sep. 25,2017 and 62/658,139 filed Apr. 16, 2018, entitled “Electric Drive Pumpfor Well Stimulation.” The disclosure of each of these applications arehereby incorporated by reference in their entirety.

BACKGROUND Technical Field

The present application relates generally to hydraulic fracturing in oiland gas wells, and in particular to an electric drive pump used to drivea fluid end for the pumping of a fracturing fluid into a well.

DESCRIPTION OF THE RELATED ART

It is difficult to economically produce hydrocarbons from lowpermeability reservoir rocks. Oil and gas production rates are oftenboosted by hydraulic fracturing, a technique that increases rockpermeability by opening channels through which hydrocarbons can flow torecovery wells. Hydraulic fracturing has been used for decades tostimulate production from conventional oil and gas wells. The practiceconsists of pumping fluid into a wellbore at high pressure (sometimes ashigh as 50,000 PSI). Inside the wellbore, large quantities of proppantsare carried in suspension by the fracture fluid into the fractures. Whenthe fluid enters the formation, it fractures, or creates fissures, inthe formation. Water, as well as other fluids, and some solid proppants,are then pumped into the fissures to stimulate the release of oil andgas from the formation. When the pressure is released, the fracturespartially close on the proppants, leaving channels for oil and gas toflow.

Fracturing rock in a formation requires that the fracture fluid bepumped into the well bore at very high pressure. This pumping istypically performed by large diesel-powered pumps in communication withone or more fluid ends. These specialized pumps are used to power theoperation of the fluid end to deliver fracture fluids at sufficientlyhigh rates and pressures to complete a hydraulic fracturing procedure or“frac job.” Such pumps are able to pump fracturing fluid into a wellbore at a high enough pressure to crack the formation, but they alsohave drawbacks. For example, the diesel pumps are very heavy, and thusmust be moved on heavy duty trailers, making transport of the pumpsbetween oilfield sites expensive and inefficient. In addition, thediesel engines required to drive the pumps require a relatively highlevel of expensive maintenance. Furthermore, the cost of diesel fuel ismuch higher than in the past, meaning that the cost of running the pumpshas increased.

To avoid the disadvantages of diesel-powered pumps, some have moved toanother option, such as electrically powered pumps. The electric fracpump configurations available now are largely comprised of existingmechanical units that are integrated into an electric system. Thispractice, however, can limit an operation's efficiency and performance.

Operators have at least two alternatives to choose from when in pursuitof a clean, electric power end pump. The first option offers adual-motor configuration coupled with up to two triplex pumps. Thislarge, industrial-sized, and air-cooled system can be capable of3600-4500 hydraulic horsepower (HHP). The second option is asingle-motor configuration. The centrally located motor is connected bytwo quintuplex pumps via a through-spindle design. This larger unit isalso air-cooled, and is capable of 6000 HHP. Existing electricconfigurations experience inefficiencies in certain key areas.Contemporary offerings for electric frac configurations are composed ofexisting components from mechanical systems that are repurposed forelectric applications. These components were not specifically built forelectric systems. Consequently, effective horsepower is decreased due todesign conflicts introducing hydraulic and mechanical resistance, aswell as accelerated wear cycles as a result of violent harmonics andmisalignments in provisional electric systems.

The inefficiencies do not end there: air-cooling solutions often leavesomething to be desired, as they are not capable of regulating thetemperatures the motors generate, especially in environments where heatis a special concern. This leads to motors running hotter, andtherefore, far less efficiently, which reduces the effective hydraulichorsepower of the entire operation. The inability to regulate runningtemperatures can also lead to premature failure.

There are other concerns regarding the integration of existingmechanical components and electrics, such as the optimization of theratios used by power end reduction gears. Electric motors are oftenmistakenly considered to produce the same results at any RPM. Eventhough they have flatter and more consistent torque and power curvesthan internal combustion solutions, this is not entirely true. Electricmotors do perform best within a certain RPM range, and contemporaryofferings have not taken full advantage of the optimization thatunderstanding provides. Reduction gear ratios that were not chosen foruse in a specific electrical application, expose motors that drive themto possible premature failure, whether it be from spinning outside ofthe optimal range, or introducing harmonic imbalances and damaging thepowertrain as a whole.

Although great strides have been made with respect to the power end of afracturing pump system, there clearly is room left for improvement inelectric drive pump fracing systems.

SUMMARY

It is an object of the present application to provide an electric drivepump system for use in well stimulation. The electric drive pump systemis configured to provide a plurality of individual motors in selectiveconfigurations that work together to provide power to a power end. Themotors are arranged around a gearbox which is used to convert the rotarymotion of the electric motors into linear motion for operation of theplungers in the fluid ends. The system includes a transmission assemblythat is composed of the gearbox and the plurality of motors. Thetransmission assembly is detachable from any power end, and is operablewith legacy power ends.

It is a further object of the present application to include atemperature regulation system that is configured to provide means ofregulating the temperature of the components within the system. Thetemperature regulation system can be configured to provide both aheating effect and a cooling effect depending on configurations.

Another object is to provide a control module for the monitoring andregulation of the various components. The control module may use anynumber of sensors to monitor operations. The motors may be regulated intheir performance as well as the temperature regulation system.Communication to and from the control module may occur through wirelessand/or wired means. Any number of input/output interfaces may beincluded to input and receive parameters and instructions.

Ultimately the invention may take many embodiments beyond the exactdepiction provided herein. This system overcomes the disadvantagesinherent in the prior art.

The more important features of the system have thus been outlined inorder that the more detailed description that follows may be betterunderstood and to ensure that the present contribution to the art isappreciated. Additional features of the system will be describedhereinafter and will form the subject matter of the claims that follow.

Many objects of the present system will appear from the followingdescription and appended claims, reference being made to theaccompanying drawings forming a part of this specification wherein likereference characters designate corresponding parts in the several views.

Before explaining at least one embodiment of the system in detail, it isto be understood that the system is not limited in its application tothe details of construction and the arrangements of the components setforth in the following description or illustrated in the drawings. Thesystem is capable of other embodiments and of being practiced andcarried out in various ways. Also it is to be understood that thephraseology and terminology employed herein are for the purpose ofdescription and should not be

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the various purposes of the present system. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present system.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. However, the invention itself, as well asa preferred mode of use, and further objectives and advantages thereof,will best be understood by reference to the following detaileddescription when read in conjunction with the accompanying drawings,wherein:

FIG. 1 is a schematic of an electric drive pump system according to anembodiment of the present application.

FIG. 2 is a front perspective view of an electric drive pump in theelectric drive pump system of FIG. 1 .

FIG. 3 is a rear perspective view of the electric drive pump of FIG. 2 .

FIG. 4 is a side view of the electric drive pump of FIG. 2 .

FIG. 5 is a rear view of the electric drive pump of FIG. 2 .

FIG. 6 is a front perspective view of a transmission assembly in theelectric drive pump of FIG. 2 .

FIG. 7 is a side view of the transmission assembly of FIG. 6 .

FIG. 8 is a rear perspective view of the transmission assembly of FIG. 6.

FIG. 9 is an alternate front perspective view of the transmissionassembly of FIG. 6 .

FIG. 10 is a front view of the transmission assembly of FIG. 9 .

FIG. 11 is an interior side view of the transmission assembly of FIG. 9.

FIG. 12 is a rear perspective view of the transmission assembly of FIG.11 .

FIG. 13 is a side section view of the transmission assembly of FIG. 12 .

FIG. 14 is a rear perspective view of the transmission assembly of FIG.13 .

FIGS. 15-18 are charts of the operative functioning of the electricmotors in various different power demand conditions.

While the application is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the application to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the application as described herein.

DETAILED DESCRIPTION

Illustrative embodiments of the preferred embodiment are describedbelow. In the interest of clarity, not all features of an actualimplementation are described in this specification. It will of course beappreciated that in the development of any such actual embodiment,numerous implementation-specific decisions must be made to achieve thedeveloper's specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, apparatuses, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms to describe a spatialrelationship between various components or to describe the spatialorientation of aspects of such components should be understood todescribe a relative relationship between the components or a spatialorientation of aspects of such components, respectively, as the assemblydescribed herein may be oriented in any desired direction.

The system in accordance with the present application overcomes one ormore problems commonly associated with conventional pumps used tostimulate a well. The electric drive pump system of the presentapplication is configured to incorporate a plurality of electric motorsto the power end or pump portion of a pump system. The motors areconfigured to operate either collectively or independently to vary thepower supplied to the power end. The electric motors may operate in anycombined manner and may operate in any sequential order. By includingsmaller motors, the motors are more easily obtained in the market,precise power requirements may be met smoothly, and overall powerconsumption may be minimized. Additionally, the electric drive pumpsystem of the present application allows end-users to almost entirelyeliminate hydrocarbon emissions by using clean-burning well gas turbinesor local industrial power sources to fuel their operations. Noisepollution is also reduced by the removal of some of the loudestequipment on the pad, and electric configurations allow for coolingsolutions that can be controlled to reduce or redirect most auditorynuisances. The electric drive pump system also has a smaller footprinton-pad than conventional pump systems. Maintenance is simplified to aconsiderable degree, since heavy, cumbersome mechanical power units arereplaced with smaller, less complex electrical power units. These andother unique features of the device are discussed below and illustratedin the accompanying drawings.

The system will be understood, both as to its structure and operation,from the accompanying drawings, taken in conjunction with theaccompanying description. Several embodiments of the assembly may bepresented herein. It should be understood that various components,parts, and features of the different embodiments may be combinedtogether and/or interchanged with one another, all of which are withinthe scope of the present application, even though not all variations andparticular embodiments are shown in the drawings. It should also beunderstood that the mixing and matching of features, elements, and/orfunctions between various embodiments is expressly contemplated hereinso that one of ordinary skill in the art would appreciate from thisdisclosure that the features, elements, and/or functions of oneembodiment may be incorporated into another embodiment as appropriate,unless otherwise described.

The system of the present application is illustrated in the associateddrawings. The assembly includes a portable base member that can rollalong the ground. The base member defines an interior volume used forstorage of various members and portions of the assembly. It alsoincludes an elevating platform in communication with the base member.The elevating platform operates between a lowered position and anelevated position. The assembly is stabilized by one or more jacks and ahitch attachment assembly configured to secure the base member to theneighboring vehicle. Additional features and functions of the device areillustrated and discussed below.

Referring now to the Figures wherein like reference characters identifycorresponding or similar elements in form and function throughout theseveral views. The following Figures describe the assembly of thepresent application and its associated features. With reference now tothe Figures, an embodiment of the electric drive pump system is hereindescribed. It should be noted that the articles “a”, “an”, and “the”, asused in this specification, include plural referents unless the contentclearly dictates otherwise.

Referring to FIG. 1 in the drawings, a schematic of an electric drivepump system for well stimulation through a power end is provided. Theelectric drive pump system 101 includes a power end 103, a transmissionassembly 105, a control module 107 and a temperature regulation assembly109. Power end 103 is configured to convert the rotational/rotary motiongenerated through transmission assembly 105 into a linear motion foroperation of plungers within one or more fluid ends. Power end 103 mayhave operate with any number of fluid ends and may be constructed from acasting or fabricated from one or more materials.

Transmission assembly 105 is releasably mounted to power end 103, andincludes a plurality of electric motors 111 and a gearbox 113 incommunication with the plurality of electric motors. The gearbox 113includes a plurality of gears for transferring rotational energy fromthe electric motors to the power end. Transmission assembly 105 alsoincludes an output spline 115 in communication with gearbox 113. Outputspline 115 is configured to transfer rotational energy from gearbox 113to power end 103. In general, transmission assembly 105 is configured tohold the drive system (motors 111 and gearing) along with coolingcomponents and sensors.

System 101 also includes control module 107 configured to regulateperformance of the plurality of electric motors 111. Electrical power isprovided to motors 111 which in turn are used to induce a torque ofselected power to rotate gears within gearbox 113. Control module 107 isused to monitor each motor's performance and control selected functions,such as power output, speed, on/off, unit temperature, and so forth. Itis understood that these are exemplary in nature and do not form anexhaustive listing of performance characteristics or functions thatmodule 107 may regulate with respect to motors 111 or system 101.Through control module 107, operation of motors 111 can be donesimultaneously as a group at a selected power level and/or independentlywherein each motor 111 is independent of the operation of other motors111 with respect to at least power output and runtime. Use of aplurality of motors 111 allows for simplification of maintenance as oneor more motors 111 may be turned off for maintenance while others remainon to maintain operation of power end 103.

It is understood that many different types of motors 111 exist and arepossible. For example, motors 111 may be AC or DC, single or multiplewound, brushed or brushless, direct drive, servo or stepper motors.Another option is that motors 111 are rare earth magnet motors whichhave increased power density. Motors 111 may be powered via batterystacks or direct feed from a main power grid. Additionally, motors 111may be powered off of waste gas from the sites. Ideally a DC powersystem is preferred.

As seen in FIG. 1 , a plurality of transmission assemblies may becoupled to drive power end 103. Motors 111 can be configured to operatein a clock-wise (CW) direction or a counter clock-wise (CCW) directionso as to collectively rotate in the same direction relative to power end103. Also seen in FIG. 1 , motors may be arranged in any manner withintransmission assembly 105. One or more motor 111 may be in directcommunication with gearing in gearbox 113. Subsequent or additionalmotors 111 used may be stacked behind an adjacent motor 111. In stackedconfigurations, the stacked motors 111 work together in a prescribedfashion according to control module 107 to apply power to gearbox 113 ata single location.

Temperature regulation assembly 109 is configured to regulate thetemperature levels of various components and members of system 101. Forexample, temperature regulation assembly 109 is configured to regulatethe temperature of power end 103 and/or transmission assembly 105.Module 107 is configured to operatively regulate performance of assembly109. One or more sensors are located throughout system 101 andcommunicate temperature readings back to module 107 and/or assembly 109.Assembly 109 includes a radiator and a cooling fan and uses any type ofworking medium (i.e. fluid) to facilitate temperature regulation.Assembly 109 may use an oil based fluid or a water based fluid as theworking medium.

Additionally, assembly 109 is configured to provide both a coolingeffect and a heating effect. For example, to optimize the performance ofsystem 101, assembly 109 can be used to heat critical components withinsystem 101 to a stable operating temperature before actuation of thesystem as a whole. Assembly 109 then may switch to a cooling mode tocool various components while in operation so as to keep the workingmedium temperature optimized.

FIGS. 2-14 are provided to show an exemplary embodiment of system 101.This embodiment is not limited to the physical characteristics sodepicted but can extend to other embodiments that are considered withinthe same functional scope and spirit of the present system.

Referring now also to FIGS. 2-5 in the drawings, views of electric drivepump system 101 is illustrated. System 101 is shown in a frontperspective view in FIG. 2 and a rear perspective view in FIG. 3 . Powerend 103 is situated between two transmission assemblies 103. Temperatureregulation assembly 109 is shown adjacent power end 103. Power end 103and temperature regulation assembly 109 are resting on a platform 117.Platform 117 is configured to elevate system 101 off the ground andprovide for the overall stability of system 101. Platform 117 isconfigured to enable mobility of system 101. System 101 may be lifted byengaging platform 117 in one method. Other methods may involve pushing,pulling, or sliding for example. Platform 117 may be a skid, trailer,operate off of wheels, or consist of any mobile type of device. As seenin the Figures, a plurality of fasteners are used to couple transmissionassembly 105 to power end 103. Assembly 105 is detachable andinterchangeable. During servicing, a single assembly 105 may be removedand replaced in a simple manner to avoid down time of the system.

Temperature regulation assembly 109 is shown in more detail from theside view of FIG. 4 and the rear view of FIG. 5 . Assembly 109 includesa radiator 119 and a fan 121. Radiator 119 may include one or more coreswith each core having the ability to cool a working medium to produce acooling effect. This effect can be provided to motors 111, transmissionassembly 105, and power end 103. Any type of working medium may be usedto pass within the core of radiator 119. It is understood that multiplecores may be used. They may be stacked together in any manner. Each ofthe plurality of cores may be either independent from one another or influid communication with each other. Independent cores permit for theuse of different working mediums. Use of different mediums may assist inproviding both heating and cooling via the same radiator. Fan 121 isconfigured to pass air onto radiator 119 so as to create an exchange ofheat.

It is worth noting as well that in FIGS. 4 and 5 the use of acirculation fan 123 is also seen in communication with transmissionassembly 105. Fan 123 is configured to selectively pass air over motors111 by having outside air (outside of transmission assembly 105) enterand mix within assembly 105. Fan 123 may work independent of assembly109 or in conjunction therewith. Module 107 may be used to regulate fan123.

Referring now also to FIGS. 6-8 in the drawings, assorted views oftransmission assembly 105 are illustrated. AS noted previously, assembly105 is detachable from power end 103. Transmission assembly 105 isdepicted herein separated therefrom as a whole unit. Transmissionassembly 105 is composed of a plurality of various components andassemblies working together to provide the transfer of rotational energyto power end 103. As seen in the side view of FIG. 7 , transmissionassembly 105 includes a motor portion 125, a gear reduction assembly127, and a planetary assembly 129. These general assemblies 125 and 127are defined in their relative location in FIG. 7 and constitute gearbox113. In the case of motor portion 125, transmission housing 131 is acover that surrounds motors 111. In FIG. 8 , output spline 115 is shown.As motors 111 rotate gearing in gearbox 113, output spline 115 rotatesand drives power end 103.

Referring now also to FIGS. 9 and 10 in the drawings, an alternate frontperspective view and front view of transmission assembly 109 isillustrated. In these Figures, a portion of housing 131 is removed forclarity and to permit a view of motors 111. Motors 111 are arranged in aradial manner about output spline 115. Fan 123 has been maintained forvisual purposes.

Referring now also to FIGS. 11-14 in the drawings, assorted views of thegearing in transmission assembly 105 is illustrated. FIG. 11 is aninterior side view of transmission assembly 105 without housing 131 andcovers associated with gearbox 113 so as to show the gearing being used.Planetary system 133 (i.e. gears) are illustrated adjacent output spline115. A bull gear 135 is shown as being located between planetary system133 and a spur gear arrangement 137. Power from motors 111 pass to thespur gear 137, to the bull gear, and then to the planetary system beforebeing output through the output spline 115. A rear perspective view isshown in FIG. 12 and is provided for perspective. The gear reduction 139is shown in more clarity.

In particular with FIG. 13 in the drawings, a side section view oftransmission assembly 105, from FIG. 11 , is provided. In this view,each of the prior gearing is shown from the side and serves to enhanceclarity in the gearing options. Planetary system 133 is understood to besuitable for any number of configurations. Output spline 115 connectstransmission assembly 105 to a crank shaft in power end 103. It isunderstood that this could also be facilitated through a key drive orflexible coupling arrangement. Motors 111 are shown in section view aswell. A drive shaft 141 is shown passing through the central part ofmotors 111. Each motor engages shaft 141. Shaft 141 engages and contactsthe spur gear 137. Also of note is the stacking capability of motors111. As shown, three motors are stacked to one shaft 141.

In particular with FIG. 14 in the drawings, a rear perspective view ofFIG. 13 is shown for clarity. In this view, a liquid port 143 is mademore visible on motor 111. Assembly 109 is able to engage motors 111through this port to provide a cooling/heating effect. Module 107 maycommunicate with motors 111 through a cable entrance point 145.Additionally, a power source may also use entrance point 145 to providepower to run motors 111. A coupling flange 147 is shown as well. This isused to facilitate mating between transmission assembly 105 and powerend 103. Contact with power end 103 may occur along this flange. Thefasteners 149 are used to secure assembly 105 in position.

Referring now also to FIGS. 15-18 in the drawings, charts of theoperative functioning of the electric motors 111 are illustrated. Asnoted previously, motors 111 may operate as a collective whole orindependent of one another. Motors 111 can be used in a continuous dutycycle or as a sequenced duty cycle to meet the requirement of the pumpsoutput. Each chart includes a table showing fourteen motors 111 whichmay be associated with a left side and a right side (the number ofmotors is exemplary only). Under each side a label of “on” and “off” isprovided. In FIG. 15 , an example of the operation of the motors 111 isprovided wherein only a small amount of power is needed. In thiscondition, only motor #1 is turned on. The others remained off.

In FIG. 16 , a 50% output is required. To produce this amount, the evennumbered motors 111 are operative while the odd numbered motors 111 aredeactivated or turned off. In this case, 50% power is provided byoperating half the motors 111 at full capacity. In FIG. 17 , 100% poweris required and therefore all motors 111 are turned on. In FIG. 18 , 70%power is required. In this example, motors 1, 5, 9, and 13 are off whilethe others are on. As seen from the exemplary charts of FIGS. 15-18 ,the power supplied can be adjusted by changing the number of motors 111turned on and the respective power output through each motor.

As alluded to above, it would appear that each motor 111 is configuredto operate in full output mode only. It is understood that the system ofthe present application may permit the motors 111 to be run at variousspeeds or power outputs. This could allow all the motors 111 to operatefor a 50% required output, where each motor 111 is producing only ½ itsmax output. An advantage of varied output motors 111 would be thatpotentially maintenance may be provided to selected motors 111 duringoperation of the fluid end without the need to completely shut downoperations as other motors 111 may be set to compensate for the neededload conditions. Naturally, the motors 111 may interact and operate inany number of different manners.

It is apparent that an invention with significant advantages has beendescribed and illustrated. The particular embodiments disclosed aboveare illustrative only, as the invention may be modified and practiced indifferent but equivalent manners apparent to those skilled in the arthaving the benefit of the teachings herein. It is therefore evident thatthe particular embodiments disclosed above may be altered or modified,and all such variations are considered within the scope and spirit ofthe invention. Accordingly, the protection sought herein is as set forthin the description. Although the present invention is shown in a limitednumber of forms, it is not limited to just these forms, but is amenableto various changes and modifications without departing from the spiritthereof.

We claim:
 1. In a pump system having a power end and a fluid end for usein hydraulic fracturing, the improvement comprising: an electric drivecomponent adapted by a gearing arrangement to deliver power to the powerend, the electric drive component including at least three electricmotors arranged in a circular layout with respect to one another, and acontrol module operably configured to regulate at least one performanceparameter of each of the electric motors, the at least one performanceparameter being selected from the group consisting of speed, power andtemperature.
 2. The pump system of claim 1, wherein the performanceparameters include both speed and power.
 3. The pump system of claim 1,wherein the performance parameters further include temperature.
 4. Thepump system of claim 1, wherein the performance parameters include allof speed, power and temperature.
 5. The pump system of claim 1, whereinthe control module is configured for selectively deactivating at leastone of the electric motors while maintaining total power output byincreasing power output from the electric motors which have not beendeactivated.
 6. The pump system of claim 1 where the improvement furthercomprises each the electric motors having a motor output shaft with aspur gear mounted thereon; and a gearbox in communication with theplurality of electric motors, the gearbox including a bull gear engagedby each of the spur gears of the plurality of electric motors for drivenrotation of the bull gear by the respective sun gears, a shaftsupporting a sun gear extending from the center of the bull gear, aplanetary gear system constructed and arranged for driven rotation bythe sun gear, an internal ring gear positioned for driven rotation bythe planetary gear system, the internal ring gear being fixedly coupledto a drive shaft for the delivery of power to the power end.